1. Field of the Invention
The present invention relates to a hybrid hot air heater incorporating a gas heater and an electric heater into one chassis.
2. Description of the Related Art
This type of conventional hybrid hot air heater as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication. No. 2000-9347 is already known. In this conventional hybrid hot-air heater, a combustion heater and an electric heater are incorporated into a chassis such that an air-blowing system is constituted by one air-blowing fan. If, in this configuration, the air-blowing system for the combustion heater and that for the electric heater are controlled by one air-blowing fan, the generated heat quantity will be different compared to when the electric heater is operated together with the combustion heater and when the combustion heater is operated alone with the electric heater not operating. This makes it necessary for different quantities of intake air to be blown into the chassis in these different cases to prevent overheating thereby making it difficult to operate the combustion heater with stability because of differences in the quantity of combusted air.
To solve this problem, an approach that was considered is one in which the combustion heater unit and the electric heater unit are arranged one over the other and each provided with an air-blowing fan as well as an inlet and an outlet in such a configuration that their air-blowing systems may be independent of each other. The inlet is mounted with an anti-dust filter to prevent dust and dirt from accumulating into the chassis of the heater.
However, if an anti-dust filter is mounted to the inlet, the quantity of air sucked into the chassis when the air-blowing fan is driven will be decreased. Therefore, to blow out a sufficient quantity of hot air from the outlet through each of the air-blowing fans, it is necessary to increase the cross-sectional area of the inlet.
However, if an inlet having a larger cross-sectional area is formed on the rear face facing toward both of the combustion heater unit and the electric heater unit, the height of the heater itself will be increased making it more difficult to use thereby creating a problem.
In view of the above problems, it is an object of the present invention to provide a hybrid hot air heater such that the heater itself is compact and easy to use.